1. Field of the Invention
This invention relates generally to automobile intruder alarm systems, and specifically to microprocessor based automobile intruder alarm systems.
2. Description of the Prior Art
With automobile thefts on the rise in many parts of the nation, vehicle theft protection devices and systems have increased in popularity. Often, however, existing systems fail to meet the standards of high protection and user convenience.
Some prior art systems use a remote control transmitter to arm and disarm the alarm. The transmitter is carried by the individual. While operable, the full potential of a remote transmitter is not being fully utilized and there are some problems.
One problem is that the prior art remote systems arm only when the doors are closed. Many alarm systems are connected to the interior or dome light as a means to sense when the door is closed. When the light is on, the system regards the door as open. This causes problems with vehicles which have delayed dome lights. The delayed dome light may remain on for about 30 seconds after the driver has left the vehicle. If so, the alarm system regards the door as still open for the 30 seconds. Consequently, the remote transmitter cannot arm the alarm system until the interior light has turned off.
Another problem with remote arming systems is that vibrations caused by the closing automobile door can often be detected by the motion and glass breakage detectors for a tiny time interval after the door is closed. If the operator arms the alarm system during this interval, the alarm system will not only be armed, but will erroneously conclude that a thief or vandal is tampering with the vehicle and accordingly sound the alarm.
Yet another problem often arises with remote controlled alarm systems. Remotely controlled alarm systems often have receiver units located within the passenger compartment of the vehicle. These receiver units are often affected by the sounding alarm. More precisely, while the alarm siren is sounding, the receiver can go out of regulation and thus either be totally unresponsive to the coded signal transmitted by the handheld receiver, or be unresponsive to the coded signal except at very short distances, often to distances that are within the confines of the vehicle.
If the operator inadvertently sets off the alarm siren, he may have to endure a full alarm sequence (often several minutes long) before he can disarm the alarm system through the use of the remote control transmitter. This several minute long vigil can result in embarrassment and undesired public attention, perhaps from a police officer.
Another problem occurs if the vehicle operator returns to his vehicle and forgets that the alarm system has been armed. When he is reminded by the sounding alarm, he can experience a sudden fright. This is annoying to the operator. Such a false sounding of the alarm is also annoying to those residing nearby. Moreover, false alarms degrade the protective value of alarm systems because the public in general is desensitized by false alarms. One prior art system employs a beeping tone upon entry of the vehicle, but this doesn't inform the driver how much time is left to disarm the system.
Alarm systems can be equipped with motion detectors. However, many of these systems respond to slight impacts with a full alarm sequence. Such impacts can be a bump from the opening door of an adjoining vehicle in a parking lot, or the bump from a vehicle attempting to parallel park in an adjoining space. Clearly, it is inappropriate to respond to such motions with a full alarm. Desensitizing the detector, however, might result in the failure of the alarm to activate when an actual theft or intrusion is taking place.
Prior art alarm systems have sirens that emit sounds with a uniform decibel level, or amplitude, but with a duration that depends upon the particular task being performed by the alarm system. Short, loud bursts, while capable of conveying information to the operator, are irritating to the operator, and bothersome to those within earshot.
Often, the operator wishes to leave his vehicle in the custody of another, such as an auto mechanic or parking lot attendant. Usually, the operator does not wish to reveal the intricacies of his alarm system to a stranger. Accordingly, prior art alarm systems have a "valet" switch which suspends the alarm system.
These valet systems have several shortcomings. First, when the valet is engaged, the vehicle indicator ceases flashing. This flashing indicator is often a light emitting diode which has a great deterrent effect. Thus, the unattended auto becomes an easy target for experienced thieves. Second, prior art valet switches will give the operator no indication that the alarm is suspended. A forgetful operator might thus suspend the alarm system for longer than desired, inadvertently exposing the vehicle to unnecessary risk.
Prior art remote activated alarm systems often have a bypass switch. These switches are secreted or otherwise cleverly concealed. They are designed to allow the operator to override the starter interrupt. The starter interrupt will disable the vehicle ignition system while and after the alarm is activated. Bypass switches are useful if the operator has misplaced his remote control transmitter or similar device used to disarm the alarm system. However, their utility is overshadowed by the security risks they pose. A clever and experienced car thief will often be able to locate the hidden bypass switch with ease.